Agreed with others, my car sat outdoors for years and had the requisite cowl/windshield leak, unlike yours, there was a good deal of damage on both pans. Wire wheel, Metal prep, POR-15 and cloth fixed it right up. In your case, attack the leaks and treat them with wire wheel, metal prep, and POR-15.
I might add I have used a wide range of POR-15 products and have been happy with all of them. If you are applying with a brush, the "standard glossy black" flows bette tyhan the others; just be sure to etch prime it before topcoat.
Chris